1. Field of the Invention
The present invention is directed to an external pump stroke indicator for use in an implanted medication infusion system of the type having a pump for conveying the medication into the patient, with an opening covered by a septum is arranged at the output of the pump.
2. Description of the Prior Art
Openings (ports) in implanted infusion systems are normally covered by a septum as well as by skin and a fatty layer of the patient. Connection of external equipment normally ensues with the assistance of a cannula that is conducted through the skin and the fat of the patient as well as through said septum. It is important that the cannula be introduced into the opening in a correct way. If the cannula is not introduced to a sufficient extent, i.e. the tip remains in the septum after penetrating the skin and the fat, no connection between the opening and the external equipment is achieved. If the external equipment is, for example, a device for measuring the flow resistance in an implanted catheter according to U.S. application having Attorney Docket No. P94,2608 corresponding to Swedish Patent Application 930 3484-1, filed simultaneously herewith, an inadequate introduction of the cannula leads to a faulty detection of a blockage in the catheter.
When, by contrast, the cannula is introduced too far into the opening, there is a risk that the tip will be destroyed and the destroyed tip will subsequently tear the septum when the cannula is withdrawn, an explantation of the infusion system thus becoming necessary.
The position of the cannula in the opening cannot be optically observed. A display or some other kind of acknowledgement that the cannula has been correctly introduced into the opening is therefore desirable. A commercially obtainable pressure transducer of the type which is used once and then is disposed of for these purposes in certain instances.